1. Field of the Invention
The present invention relates to a push switch used in input operation sections of various electronic apparatuses and a method for manufacturing the same.
2. Background Art
Recently, a push switch having a protrusion portion in the operation part thereof has been mounted in various electronic apparatuses. FIG. 5 is a sectional view of a conventional push switch. FIG. 6 is an external perspective view of the conventional push switch.
Case 1 has a recess portion that opens on the top surface and is formed of resin. On the inner bottom surface of the recess portion of case 1, center contact 2 and outer contacts 4 are fixed. Center contact 2 is connected to first terminal 2A led out from case 1, and outer contact 4 is connected to second terminal 4A led out from case 1. Movable contact 5 formed of a metal thin plate and having a circular dome shape projecting upward in the center thereof is accommodated in the recess portion of case 1.
Protective sheet 7 is formed of an insulating film such as a polyimide film having adhesive agent 8 on the entire lower surface. Protective sheet 7 is attached to the upper end of case 1 with adhesive agent 8 so as to cover the recess portion of case 1.
Operating protrusion portion 10 is provided in a part corresponding to the center position of movable contact 5. The corresponding part of protective sheet 7 is plastically deformed into an upwardly convex shape, and accommodating member 11 processed to be formed in a columnar shape is pushed into from the lower surface side of protective sheet 7. Thus, protrusion portion 10 is formed.
The top surface portion and peripheral portion of accommodating member 11 are adhesively fixed to protective sheet 7 with adhesive agent 8.
Next, an operation of the conventional push switch is described. When a user operates to depress an operation button (not shown) at an electronic apparatus side, protrusion portion 10 is depressed by the lower surface of the operation button, and force is applied to movable contact 5 via protrusion portion 10. When the force exceeds a predetermined size, the center portion of movable contact 5 is reversed with a click feeling, and the lower surface of the center portion of movable contact 5 is brought into contact with center contact 2. Consequently, center contact 2 and outer contacts 4 are electrically connected to each other via movable contact 5, thus bringing terminal 2A and terminal 4A into electrical conduction. When the force is removed, movable contact 5 returns by itself to the original shape by resilient force of itself, and terminal 2A and terminal 4A return to a state before the operation in which they are electrically independent from each other.
In a conventional push switch, accommodating member 11 of protrusion portion 10 is adhesively attached to protective sheet 7 with adhesive agent 8. Therefore, when a pressing operation is repeated, the adhesive strength is weakened, and protective sheet 7 and accommodating member 11 may be peeled off from each other. Furthermore, after the recess portion is formed by plastically deforming protective sheet 7 such that it corresponds to the outer shape of accommodating member 11, accommodating member 11 is inserted into the recess portion.
In order to improve the adhesive strength of accommodating member 11, it is important to insert accommodating member 11 into the recess portion of protective sheet 7 without a gap. In order to do so, high accuracy of protective sheet 7 is required in manufacturing. Therefore, it is necessary to finely adjust pressing conditions such as temperature and time when the recess portion of protective sheet 7 is formed.